📝 SummarXiv

Abstract

We present a comprehensive statistical analysis of brown dwarf companions to investigate the physical mechanisms responsible for the observed "brown dwarf desert", the notable paucity of brown dwarf companions, at orbital separations between 0.1 and 5 AU. Using a sample of 108 confirmed brown dwarf companions from the NASA Exoplanet Archive with masses between 13-80 Jupiter masses and orbital semi-major axes between 0.1-5.0 AU, we employ Kolmogorov-Smirnov statistical (KS) tests to compare observed orbital distributions with three proposed formation scenarios: (A) disk migration with stellar infall, (B) core accretion with mass-dependent survival probability, and (C) formation bias through dynamical migration. Our systematic grid-search analysis spans 27 parameter combinations for disk migration, 9 for core accretion, and 3 for formation bias models. The disk migration model provides the best statistical fit to observations (KS statistic = 0.100, p-value = 0.216), with optimal parameters {\mu}_rate = 0.5, {\sigma}_rate = 0.5, and t-myr = 0.5. The formation bias model achieves intermediate performance (KS = 0.173, p-value = 0.005) with optimal migration fraction p_move = 0.05, while the core accretion scenario shows the poorest fit (KS = 0.417, p-value = 3.5{\times}10^-17) despite its theoretical appeal. Our results suggest that brown dwarfs primarily form at wide separations and undergo limited inward migration, challenging scenarios that invoke in-situ formation through core accretion processes at close orbital separations.